1. Field of the Invention
The present invention relates to an electron emitter having a first electrode and a second electrode which are formed on a substance serving as an emitter.
2. Description of the Related Art
Recently, electron emitters having a cathode electrode and an anode electrode have been finding use in various applications such as field emission displays (FEDs) and backlight units. In an FED, a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of phosphors are positioned in association with the respective electron emitters with a predetermined gap left therebetween.
Conventional electron emitters are disclosed in the following documents 1 through 5, for example. All of these disclosed electron emitters are disadvantageous in that no dielectric material is employed as a substance serving as an emitter, a forming process or a micromachining process is required between facing electrodes, a high voltage needs to be applied to emit electrons, and a panel fabrication process is complex and entails a high panel fabrication cost.
It has been considered to use a dielectric material as a substance serving as an emitter. Various theories about the emission of electrons from a dielectric material have been presented in the following documents 6 through 8:
[Document 1]
Japanese laid-open patent publication No. 1-311533
[Document 2]
Japanese laid-open patent publication No. 7-147131
[Document 3]
Japanese laid-open patent publication No. 2000-285801
[Document 4]
Japanese patent publication No. 46-20944
[Document 5]
Japanese patent publication No. 44-26125
[Document 6]
Yasuoka and Ishii, “Pulse electron source using a ferrodielectric cathode”, J. Appl. Phys., Vol. 68, No. 5, p. 546–550 (1999)
[Document 7]
V. F. Puchkarev, G. A. Mesyats, On the mechanism of emission from the ferroelectric ceramic cathode, J. Appl. Phys., Vol. 78, No. 9, 1 Nov., 1995, p. 5633–5637
[Document 8]
H. Riege, Electron emission ferroelectrics—a review, Nucl. Instr. and Meth. A340, p. 80–89 (1994)
As shown in FIG. 39, when an upper electrode 204 and a lower electrode 206 are formed on a substance (emitter) 202 serving as an emitter in a conventional electron emitter 200, the upper electrode 204 in particular is formed in intimate contact with the emitter 202. A point where electric field concentrates is a triple point made up of the upper electrode 204, the emitter 202, and the vacuum, and corresponds to a peripheral edge portion of the upper electrode 204.
However, since the peripheral edge portion of the upper electrode 204 is held in intimate contact with the emitter 202, the arrangement suffers a problem in that the degree of electric field concentration is small and the energy required to emit electrons is small. Furthermore, because an electron emission region is limited to the peripheral edge portion of the upper electrode 204, the overall electron emission characteristics tend to vary, making it difficult to control the emission of electrons and also making the electron emission efficiency low.